Health and Human Services Secretary Kathleen Sebelius asked the 13-member commission to review the possible medical experiment after critics raised questions about whether it would be ethical. They questioned whether the risks of the testing were necessary given that an anthrax attack may never happen.

"This assignment was one of the most difficult that any bioethics commission has been given," Gutmann says.

Anthrax has long been considered one of the most likely weapons a bioterrorist might use. It's relatively easy to make and spew over a large area. And the toxins produced by anthrax spores can be deadly, especially if inhaled.

"We want to make sure we're taking care of the kids," says Daniel Fagbuyi of the Children's National Medical Center, who chaired a federal panel that started the push to study the anthrax vaccine in kids.

The vaccine's been given to more than 1 million adults in the military, but no one knows how well it would work in children.

"We want to know what we're doing to them. Does this really work? And how does it work? What's the body's immune response to it? Those are the types of things that we need to glean," Fagbuyi says.

But other experts are skeptical. They wonder whether it's worth exposing kids to the vaccine for a theoretical risk, which means they won't directly benefit. So Sebelius asked the commission to vet the proposal.

"There is something to be gained by going ahead with research on children. There is a common good to be gained in being prepared," Gutmann says.

But Gutmann says that has to be weighed against an important principle.

"We have a long-standing ethical requirement in this country that children not be used merely as means for the public good," Gutmann says.

So after holding hearings and picking apart the scientific and ethical nuances, the commission outlined a series of steps researchers would have to take before any testing on children would be ethical.

Those steps would have to include research to convincingly show that children would face no more than "minimal risk." Gutmann defines that as the "level that a child routinely encounters in daily life for a medical check-up that poses absolutely no substantial risk or threat to the child."

In addition to modeling and testing in animals, the commission said researchers should first try testing the vaccine in younger adults. If that goes OK, they might try studying the vaccine on the oldest kids and work their way down very slowly to the youngest.

Other experts praised the commission's conclusions.

"We can overreact to the threat of bioterrorism and other terrorist attacks," says Lawrence Gostin of Georgetown University. "When we really don't know whether, when or if we will get any kind of an attack, it seems to me that we really do need to have very rigorous ethical safeguards," Gostin says.

But those pushing for the testing, like Fagbuyi, are disappointed. He's worried what might happen if there's an attack while we're waiting. Parents will be frantic but doctors won't know what to tell them about how well the vaccine works or whether it's safe.

"During a time of an emergency when there's enough chaos going on and discord, is that the time we really want to be explaining that, 'Well, we don't have all the evidence at this time, and we could have done this earlier, and we did not'?"

The Department of Health and Human Services, which will make the final decision about whether to move forward with the testing, issued a statement saying officials would review the commission's report.

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STEVE INSKEEP, HOST:

President Obama's administration has laid out guidelines today for conducting controversial medical research. The federal government is considering testing the anthrax vaccine in children to try to prepare for a bioterrorist attack.

As NPR's Rob Stein reports, a presidential commission says several steps would have to be taken before any testing. And the report raises questions about whether such tests are ethical.

ROB STEIN, BYLINE: In the world of bioterrorism, anthrax is one of the scariest threats. It's relatively easy to make and spread over a large area. And Daniel Fagbuyi says anthrax can hide for long periods in dormant spores that release potent toxins.

DANIEL FAGBUYI: At some point it hatches. When it does hatch, it can cause invasive disease, meaning like pneumonias and bacterial infection in the body that can lead to death. And that's why anthrax is very deadly and something of great concern to us.

STEIN: Fagbuyi is a pediatrician. He led a federal panel that started the push to study the anthrax vaccine in kids. More than a million adults in the military have gotten the shot, but Fagbuyi says no one knows how well it works in children.

FAGBUYI: The main priority is protecting children. I mean we're strong advocates for our kids, our precious gems, and we want to know what we're doing to them. Does this really work and how does it work? What's the body's immune response to it? Those are the type of things that we need to glean from those studies.

STEIN: But other experts are skeptical. They question exposing kids to the vaccine for something that may or may not actually ever happen. So federal officials asked for advice.

AMY GUTMANN: This assignment was one of the most difficult that any bioethics commission has been given.

STEIN: Amy Gutmann chairs the Presidential Commission for the Study of Bioethical Issues.

GUTMANN: There is something to be gained by going ahead with research on children. There is a common good to be gained in being prepared.

STEIN: But Gutmann says that has to be weighed against another important principle.

GUTMANN: We have a longstanding ethical requirement in this country that children not be used merely as means for the public good.

STEIN: Especially when they won't directly benefit themselves. So after holding four public meetings and picking apart the ethical nuances, the commission is releasing its conclusions.

GUTMANN: We concluded that the federal government would have to take multiple steps before anthrax vaccine trials with children could be ethically considered. It would not be ethical to do it today.

STEIN: The first thing that would have to be done would be a lot more research - research that convincingly shows kids would face no more than what's considered minimal risk.

GUTMANN: Minimal risk being a level that a child routinely encounters in daily life or a medical checkup that poses absolutely no substantial risk or threat to the child.

STEIN: So researchers should first try testing the vaccine in younger adults. If that goes OK, they might try it on the oldest kids and then work their way down very slowly to the youngest. Other experts praise the commission's conclusions, like Lawrence Gostin of Georgetown University.

LAWRENCE GOSTIN: We can overreact to the threat of bioterrorism and other kinds of terrorist attacks when we really don't know whether when or if we will get any kind of an attack. It seems to me that we really do need to have very rigorous ethical safeguards.

STEIN: But those pushing for the testing, like Fagbuyi, worry what might happen if there's an attack in the meantime.

FAGBUYI: During the time of an emergency, when there's enough chaos going on and discord, is that the time we really want to be explaining that, well, we don't have all the evidence at this time and we could have done this earlier and we did not?

STEIN: Officials at the Department of Health and Human Services say they will review the commission's report before making a decision about whether or how to proceed with testing the anthrax vaccine in children. Rob Stein, NPR News, Washington. Transcript provided by NPR, Copyright NPR.